(c) No person may cause, suffer, allow or permit emissions of
nitrogen oxides, calculated as nitrogen dioxide, from any "front
fired" steam generating unit of more than 600,000 lbs/hour maximum
continuous steam capacity to exceed 0.5 lbs/ million Btu heat
input, maximum two-hour average, at maximum steam capacity. A
"front fired" steam generating unit is defined as a unit having all
burners installed in a geometric array on one vertical firebox
surface.

(d) No person may cause, suffer, allow or permit emissions of
nitrogen oxides, calculated as nitrogen dioxide, from any
"tangential fired" steam generating unit of more than 600,000
lbs/hour maximum continuous steam capacity to exceed 0.25 lbs/
million Btu heat input, maximum two-hour average, at maximum steam
capacity. A "tangential fired" steam generating unit is defined as
a unit having burners installed on all corners of the unit at
various elevations.

(e) Existing gas fired steam generating units of more than
600,000 lbs/hour but less than 1,100,000 lbs/hour maximum
continuous steam capacity are exempt from Rule 131.09.00.001
provided the total steam genreated from the unit during any one
calendar year does not exceed 30 percent of the product of the
maximum continuous steam capacity of the unit times the number of
hours in a year. Written records of the amount of steam generated
for each day's operation shall be made on a daily basis and
maintained for at least three years from the date of each entry.
Such records shall be made available for inspection by employees of
state and local agencies during regular business hours

Any person required to modify one steam generating unit to
comply with Rule 131.09.00.001 shall be in compliance by July 1,
1974. Any person required to modify two or more steam generating
units to comply with Rule 131.09.00.001 shall achieve compliance on
at least 50% of such units by July 1, 1974, and shall achieve total
compliance by July 1, 1976. On or before December 1, 1972, any
person affected by Rule 131.09.00.001 shall submit to the Texas Air
Control Board a writtin report of his compliance status, including
but not limited to, the minimum time required to design, procure,
install and test abatement equipment or procedures. Thereafter,
progress reports shall be submitted to the Board every six monthis
no later than June 1 and December 1 of each year until compliance
is achieved.

Persons affected by Rule 131.09.00.002 shall be in compliance
with the provisions of Rule 131.09.00.002 not later than December
31, 1973. On or before September 15, 1972, any person affected by
Rule 131.09.00.002 shall submit to the Board a written report of
his compliance status, including but not limited to the minimum
time required to design, procure, install and test abatement
equipment or procedures. Thereafter, progress reports shall be
submitted to the Board every four months, not later than January
15, May 15 and September 15 of each year until compliance is
achieved.